This invention relates to a method of and an apparatus for measuring characteristic features of fibrous material, and it relates in particular to the measurement of the quantity of fibers in textile slivers.
Attempts have been made for a relatively-long time and corresponding methods and apparatus have been developed to determine the quantity of fibers in textile slivers by means of ultrasonics. In this respect, reference is made, for example, to the Heller U.S. Pat. No. 2,966,057, and to the publication by Bobrov, Gorelik and Volosmikov, Teknologia Tekstilnov Promystchlennosti No. 4 (1973), page 115. However, these attempts have been unsuccessful in producing an apparatus of satisfactory accuracy and reliability. An essential reason for this failure lies in the high interference capability of sound waves. In this regard, certain resonances arise in any arrangement which severely disturb the linear or monotonic relationship between fiber quantity and the magnitude of the sound signal.
Another problem which is encountered in determining the quantity of fibers using ultrasonics relates to the fact that even very small openings are sufficient to produce a false or inaccurate measurement, if sound waves are able to pass through these openings from the source to the pick-up without fully penetrating the fibrous material.